1. Field of the Invention
The present invention generally relates to a plasma generating apparatus and method, and more particularly, to a plasma generating apparatus and method which can be suitably applied to semiconductor process technologies.
In recent semiconductor process technologies using a plasma generator, there is a need for plasma etching under a high-vacuum condition, namely anisotropic etching capable of establishing a fine structure in semiconductor devices. However, as the degree of vacuum becomes higher, it becomes more difficult to generate high-density plasma. For generating a stable and high-density plasma, an auxiliary apparatus generating a magnetic field is required in addition to a plasma source. Such an additional apparatus may cause complexity of the plasma generator, and may increase the cost of the plasma generator. Thus, the semiconductor devices manufactured by using the above generator may be very expensive.
On the other hand, as a wafer size is increased, a larger volume of a plasma generator chamber is required. However, in such a large-volume chamber, power supplied to the plasma is dropped by reflection, etc., caused by the plasma generating process, whereby the plasma immediately dies out. Therefore, it is hard to generate uniform and stable, high-density plasma throughout the large volume of the chamber. Thus, it is desired to realize a superior plasma generator which can easily generate and maintain uniform and high-density plasma throughout the large volume of the chamber under the high-vacuum condition.
2. Description of the Prior Art
Conventionally, there are two major methods for plasma generation: 1) a capacitive-coupling method (RIE); and 2) an inductive-coupling method (ICP, etc.).
In the capacitive-coupling method, an electric field generated between electrodes enables superior uniformity of plasma density within a generator chamber. Thus, this method is suitable for anisotropic etching. However, in order to generate stable, high-density plasma under a high-vacuum condition with a larger-sized wafer and a larger-volume chamber, a significantly high voltage needs to be maintained across the electrodes. Therefore, dropping of power supplied to the plasma, which is caused by reflection, etc., during processing, causes the plasma to immediately die out. Thus, a high-power RF (radio frequency) power supply is required. To satisfy this requirement, heat sink control for external devices and reinforcement for generator construction are necessary, and thus the total cost of the plasma generator may increase.
On the other hand, the inductive-coupling method enables generation of relatively-high-density plasma. However, the power is supplied to the plasma from a coil (antenna) wound around the generator chamber, so that the plasma density in an outer part of the chamber is different from that in an inner part thereof and the generated plasma does not have a direction applicable to anisotropic etching. Therefore, another bias power supply, in addition to a power supply supplying the above-mentioned power to the plasma from the coil, is needed to obtain uniform plasma density throughout the large volume of the chamber and to orient the plasma stream in a desired direction. Furthermore, a control operation is needed to control phases of signals from the power supply for generating the plasma and the additional bias power supply. As a result, the above may cause controlling methods and configuration of the plasma generator to be complex, and thus a complicated operation on a variety of parameters is needed to supply stable plasma.
In the case of generating plasma by the capacitive-coupling method, the plasma thus generated has a good uniformity and is suitable for the anisotropic etching. However, when processing with a larger-sized wafer and a larger-volume chamber, there is a disadvantage in that it is difficult to generate and maintain stable, high-density plasma under the high-vacuum condition.
In the case of generating plasma by the inductive-coupling method, the plasma thus generated has an advantage of having a relatively high density. However, there are disadvantages in that the plasma is not uniform and the direction of the plasma stream is uncontrollable. Furthermore, in order to generate the plasma having both uniformity and direction throughout the large-volume chamber, it is necessary to install the coil and an external device such as the bias power supply.